Этот код отвечает на этот вопрос в совершенстве:
String word = ""; int val = 0;
while(!word.matches("quit"))
{
System.out.println("Enter the word to be searched for");
Scanner input = new Scanner(System.in);
word = input.next();
Scanner file = new Scanner(new File("newFile.txt"));
while(file.hasNextLine())
{
String line = file.nextLine();
if(line.indexOf(word) != -1)
{
System.out.println("Word EXISTS in the file");
val = 1;
break;
}
else
{
val = 0;
continue;
}
}
if(val == 0)
{
System.out.println("Word does not exist");
}
System.out.println("-------continue or quit--- enter continue or quit");
word = input.next();
}